I've always love nature. Nature has opened my eyes to the wonders of the world. There's always something new to discover and learn. Nature is always full of possibilities. This blog is a documentation of the animals I encountered on my nature explorations and I welcome all to share in my appreciation of Singapore's wild fauna.

Saturday, November 15, 2008

Devadatta argyoides

Competition to find a mate and reproduce the next generation is always very intense in the animal kingdom. Sometimes even a successful mating might not necessary guarantee the offsprings are sired by the original male.

Males of dragonflies and damselflies are especially adapted to displace the sperm of the previous male from a female. The discovery of sperm displacement in odonates by Prof. Jonathan Waage in 1979 is considered a significant finding in odonatology. Since then, it is now known there are four distinct ways a male can displace a rival male’s sperm: 1) physical removal by means of hooks or horns on the penis; 2) moving rivals’ sperm to sites in the females where its least likely to be used; 3) stimulation of female to induce sperm expulsion; 4) flushing out of rival’s sperm using the copulating male’s sperm.

These are fascinating behaviours. An earlier post mentioned this casually. Recently, I observed the copulation of Devadatta argyoides, enabling me a better understanding of sperm displacement.

Devadatta argyoides is from the family Amphipterygidae. This is a small and primitive family with only one species present in Peninsular Malaysia and Singapore. In fact Singapore is the type locality for this damselfly. It is rather common and usually found perching near small forest streams.

This couple had just gotten into tandem when I first spotted them. The male then flew with the female in tow for a short distance before perching above the stream. Slowly the female bent her abdomen to form the 'wheel’ thus interlocking their genitalia. Almost immediately, the male started displacing rivals’ sperm. This can be seen clearly by the male abdomen’s active movement. It lasted for about 2-3 minutes before the male stopped moving to transfer in his own sperm.

After copulation, the couple separated with the female flying off a distance away. The male did not seem interested in mate guarding nor did the female oviposit after I followed her for almost 10 minutes. I’m not familiar with the mating system of D. argyoides. Perhaps during this post-copulatory rest, the female was assessing the male’s guarding capacity, or the suitability of ovipositing site, or she’s manipulating the recently received sperm for fertilisation and evaluating its quality. The mating systems in odonates are varied with six systems currently recognised by scientists. There are lots more to discover on odonates mating behaviour especially species rarely encountered due to their elusive nature.

Pictures and video taken at: Bukit Timah Nature Reserve, October & November 2008

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Hi matinggeckos,Can I use your damselfly pictures in my poster (with citation)? The theme is to promote biodiversity in Singapore. It is part of my course assessment in NUS.Your permission will be greatly appreciated. Thank you.Regards,Weixin